-s, --shared
Obtain a shared lock, sometimes called a read lock.
读锁
-x, -e, --exclusive
Obtain an exclusive lock, sometimes called a write lock. This is the default.
写锁
-u, --unlock
Drop a lock. This is usually not required, since a lock is automatically dropped when the file is
closed. However, it may be required in special cases, for example if the enclosed command group may
have forked a background process which should not be holding the lock.
-n, --nb, --nonblock
Fail (with an exit code of 1) rather than wait if the lock cannot be immediately acquired.
非阻塞
-w, --wait, --timeout seconds
Fail (with an exit code of 1) if the lock cannot be acquired within seconds seconds. Decimal fractional
values are allowed.
超时时间
-o, --close
Close the file descriptor on which the lock is held before executing command. This is useful if command
spawns a child process which should not be hold ing the lock.
-c, --command command
Pass a single command to the shell with -c.
要执行的命令